Project Summary The current study proposes to examine associations between daily marijuana use and other substance use among African American adolescents, and to identify potential mechanisms underlying concurrent substance use among this population. This proposal addresses the emerging trend of disproportionate increases in rates of marijuana use among African American youth relative to those of Whites. The scientific premise of my proposal is that the disproportionate increases in marijuana use among African American youth will contribute to increased substance-related consequences among this group because marijuana use is strongly associated with concurrent use of alcohol and tobacco. Concurrent substance use is particularly concerning among adolescents because it is associated with more severe long-term consequences than single substance use including psychological distress and delinquency. Given the relationship between adolescent marijuana use and concurrent substance use, my proposed project examines patterns of single and concurrent marijuana use and their association with substance-related consequences among adolescent substance users by race. The current study will employ text-message-based daily diary surveys among a community-based sample of current African American and White substance users to quantitatively compare current patterns of marijuana, alcohol and tobacco use, and consequences associated with specific patterns of use. My specific hypotheses are: 1) marijuana use will be more strongly associated with tobacco use and no concurrent use among African American adolescents, but more strongly associated with alcohol use among white adolescents; 2) compared to marijuana only use, concurrent use of marijuana and other substances will be more strongly related to consequences among African American adolescents than White adolescents. I will also conduct qualitative interviews among a subsample of African American youth to identify potential mechanisms that differentiate users of marijuana only from concurrent users of marijuana and other substances. The long-term goal of this research is to identify African American adolescents at greatest risk for substance-related consequences and illuminate mechanisms underlying risk in order to inform prevention programming.